How to set x axis value as tooltip in flot charts textual data

Question

I tried with following code in Flot char to draw a chart. Chart is plotting as expected but not tooltip

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Answer 1

The solution is using tooltipOpts -> content method with a callback function to properly return dynamic data to the label.

I figured out that passing a 4th argument to the callback function of the "tooltipOpts" actually gives you the whole data object from which the chart/graph is constructed from. From here, you can easily extract the X axis labels, using the second argument of this same function as the index of the label to extract.

EXAMPLE:

Data object I'm passing to the plot function:

[
    {
        data: [[1,47478],[2,24500],[3,40177],[4,10512],[5,10512],[6,10512],[7,43439]],
        points: { show: true, radius: 3},
        splines: { show: true, tension: 0.45, lineWidth: 0, fill: 0.4}
    }
],
{
    colors: ['#0cc2aa'],
    series: { shadowSize: 3 },
    xaxis: {
        show: true,
        font: { color: '#ccc' },
        position: 'bottom',
        ticks: [[1,'Thursday'],[2,'Friday'],[3,'Saturday'],[4,'Sunday'],[5,'Monday'],[6,'Tuesday'],[7,'Wednesday']],
    },
    yaxis:{ show: true, font: { color: '#ccc' }, min:1},
    grid: { hoverable: true, clickable: true, borderWidth: 0, color: 'rgba(120,120,120,0.5)' },
    tooltip: true,
    tooltipOpts: {
        content: function(data, x, y, dataObject) {
            var XdataIndex = dataObject.dataIndex;
            var XdataLabel = dataObject.series.xaxis.ticks[XdataIndex].label;
            return y + ' impressions for all of your posts on ' + XdataLabel;
        },
        defaultTheme: false,
        shifts: { x: 0, y: -40 }
    }
}

Chart rendered from the above data object:

As you can see on the image preview, the logic used to render the label's content dynamically form the actual data is this:

tooltipOpts: {
    content: function(data, x, y, dataObject) {
        var XdataIndex = dataObject.dataIndex;
        var XdataLabel = dataObject.series.xaxis.ticks[XdataIndex].label;
        return y + ' impressions for all of your posts on ' + XdataLabel;
    },
    defaultTheme: false,
    shifts: { x: 0, y: -40 }
}

Answer 2

The easiest way to solve your problem is to replace the content string with a callback:

tooltipOpts : {
        content : getTooltip,
        defaultTheme : false
      },

I defined getTooltip to get your desired output:

function getTooltip(label, x, y) {
    return "Your sales for " + x + " was $" + y; 
}

It works, as you can see in the updated jsFiddle, but you may want to consider the advice of captain, in comments, and see what's best in your case.